Mounting for tubular resistors



APril 1960 A. c. SCRIBNER 2,931,997

MOUNTING FOR TUBULAR RESISTORS Filed Dec. 23, 1957 I NV EN T OR. Jen/0e(array 'ce/ade'e ,iJ/ATTORNEY 2,931,991 MOUNTING FOR TUBULAR RESISTORSArthur Clayton Scribner, Rowayton,

Ward Leonard Electric Co., corporation of New York Conn., assignor toMount Vernon, N.Y., a

This invention relates to tubular resistor mountings and the mounting ofa plurality of resistors in compact relation.

An object of this invention is to mount tubular electrical resistorunits with high heat dissipation from the resistors.

Another object of the invention is to increase the flow of the coolingmedium passing through and over a number of closely mounted tubularresistors.

J Another object of the invention is to provide a mounting for tubularresistors that does not obstruct the flow of air around and through theresistors.

Another object of the invention is to increase the wattage dissipationof heat from a bank of resistors while maintaining resistors within theoperative temperatures.

Another object of the invention is to provide a mounting for tubularresistors that is inexpensive and on which it is easy to mountresistors.

Another object of the invention is to provide for thermal changes in thedimensions of the mounting and resistor and to maintain the stress onthe tubular resistor at a minimum. 7

*Other and further objects will become apparent from the followingdescription taken in connection with the drawings, in which- Fig. 1 is afragmentary view of a bank of tubular resistors mounted in accordancewith the invention.

Fig. 2 is a fragmentary top view of a plurality of rows of tubularresistors.

Fig. 3 is a sectional view of the tubular resistor and the mountingtaken along lines 3--3 of Fig. 1. 1

Figs. 4 and 5 illustrate the spring mounting brackets. Fig. 6illustrates a portable rheostat utilizing the invention.

Fig. 7 is a fragmentary sectional view of the mounting of the supportingstrip to the frame; and

'Figs. 8 and 9 are fragmentary views of another embodiment of themounting.

In Fig. 6 a rheostat unit is illustrated in which a plurality of rows ofresistors is provided which may be connected in and out of the circuitto vary the resistance of the circuit for various purposes. A frame 10is provided for supporting the units of the rheostat and has crossmembers 11 spaced on opposite sides of the frame for supporting thecross supporting strips 12 upon which the resistors are mounted in rows.Each resistor row comprises a plurality of individual resistors 13, eachseparately mounted on the cross supporting strips 12 by clips 14. Thecross strips 12 are thin, flat steel pieces with the plane of the stripextending parallel to the axes of the resistors so as to present aminimum resistance to the flow of air. The strips 12 are secured at eachend to the cross members 11 by means of angles 12b welded to the strips12 and bolted to the cross pieces 11 (Fig. 7).

The strips 12 are arranged to support a plurality of rows of resistorsas illustrated in Figs. 1, 2 and 7. The resistors are solely secured tothe strips 12 by means of tend in a plane parallel to the axis of the2,931,997 l atented Apr. 5, v1960 the spring mounting brackets 14. Theresistors 13 are spaced to provide room for the radiation anddissipation of heat by convection current passing around and between theresistors.

The brackets 14 (Figs. 4 and 5) are formed from a resilient steel wireformed with legs 15 and 16 connected at one end by a U-shaped member 17and at the other end by a clip 18. The legs 15 and 16 are preferablyspot welded to the clip 18 on opposite sides of the mounting opening 19to secure the end of the legs 15 and 16 together and to provide amounting for the bracket 14. The legs of the bracket are parallel andformed in a generally U-shape with the legs 15 and 16 extendinggenerally parallel to the plane through the clip 18 along the portions15a and 16a and then having portions 15b and 16b at an angle theretoconnected by the U-shaped portions and 160. The mounting bracket 14 isresilient and the leg portions 15b and 16b may be pressed towards theleg portions 15a and 16a under pressure.

The brackets 14 are mounted in opposite ends of the tubular member 13with the bracket in a compressed condition to fit in the end of thetube. Under the compresssive force applied to the bracket 14, the legs15a,. 16a and 15b, 16b engage the inner wall 13a of the tubu-- larmember along a substantial portion of their respec tive lengths. Theexpansive force of the bracket fric 17 is bent at an angle to the legs15!) and 16b to provide:

a means for preventing the tubular resistor from sliding:

off the end of the brackets and engaging the strips 12.. As indicated inFig. 7, the bracket is fastened to the strip 12 so that the member 17 ispositioned between the strip- 12 and the end of the tubular resistor.Normally the frictional force of the legs of the bracket is suflicienttw hold the resistor in place, however, under extreme vibration slippagemay occur. The U-shaped portion 17 connecting the other ends of thewires 15 and 16 engages the end of the tubular resistor so that theresistor is held against axial movement by the U-shaped portion 17.

With the clip 18 in a plane parallel to the legs 15 and 16, the clipextends parallel to the axis of the tubular resistor, so that the clipis extending in the direction of the air flow through and over thetubular resistor. The clip 18 is secured to the strips 12 by means ofmachine screws 20 fitting snugly in the openings 19 and threaded intoopenings in the strips 12. The strips extubular resistor so that each ofthe mounting members presents the portion of the member having thesmallest dimension to the air flow, and thereby reduces the resistanceto the air flow to a minimum. The wire brackets 14 form openings 22, 23and 24 in the bore 21 of the tubular members through which air mayreadily fiow, thus permitting substantial quantities of air to flow upthrough the center of the tubular resistor to remove heat from the innerwalls.

The supporting strip has its narrow dimensions across the air flow andthe brackets are mounted on the channel so that as each strip crossesthe end ceramic portion of the resistor it does not cross the bore 21.Thus, the obstruction to the air flow through the center of the resistorand around the outer surface is reduced to a minimum permitting a morerapid flow of air past the resistor and reducing the effect of pocketingor stagnant areas adjacent to the resistor which would create localoverheating due to the non-convection of air currents past the heatedportions of the resistor.

The bracket 14 is made of a resilient spring steel or suitable resilientmaterial and provides a resilient mounting for the tubular resistor,isolating the resistor from shocks and vibrations that may be applied tothe frame of the rheostat. The bracket forms a firm attachment so thatthe resistor does not vibrate or move on the mounting. Also, themounting provides for readjustment to the variations in temperature ofthe frame members and mounting brackets without applying strain to theresistors. Thus, the "resistors are isolated from vibrational andthermal changes, thereby reducing the susceptability of the resistors tobreak down from physical forces applied to the frame.

The topv framework of the cross .strip portions 12 and the brackets 14forms air spaces 26 and 27 between the resistors to permit the easy flowof cooling air in a direction parallel to the inner spaces 22, 23 and,24 within the tubular resistors. This increased airflow increases theheat; dissipation from each resistor and from the resistors assembled ina group in'accordance. with the teachings of this invention. In thepreviously described, embodiment the rows of resistors are parallel.However, the invention provides for the arrangement of the rows with.theresistors end to end. With the strip 12 parallel to the. air flow,the spaces 27 between the resistors areunob structed and the air canflow smoothly past one resistor and on to the next, resistor to removethe heat dissipated. Also, the. air can ..l1ow through and out of. the

, end of the bore to impinge on the, succeeding resistor.

This increase in heat dissipation permits a reduction in the number ofresistors or an increase in the Wattage of a given bank of resistors,Thus, a higher load capacity and a structurally superiorrheostat may beprovided without an increase in cost. Themounting, in addition toincreasing the heat dissipation, also reduces thefailure of resistorsdue to physical forces applied thereto, and thus reduces themaintenancev and replacement of parts in the rheostat.

Although the formof the. clip shown .inFigs. 4 and is the preferredembodiment, the invention may .bepracticed in other forms. In FigsQ'Sand, 9 a clip 30 is formed from resilient sheet materiahsuch assteel-,-' and is bent in a V-shaped toform portions 31 and, 3,2. Theseportions have a common edge .33 and end edges 34 and35, re-

spectively, which press against the inner bore 13a of they resistorunder the resilient compression of, the clip, The portion 31 is extendedto form a mounting means 36 with a hole 37 for a fastening bolt. The,portion 32 has an angularextension 38. similar to the portion 17 of theclip 14. to prevent, thev resistor .from slipping against the mountingstrip under undue vibration. Also, types of resistors other than ceramicresistors may be mounted in this manner. 7

Although in the foregoing description, of the apparatus the resistorshave been'described as being cooled by air,

it is understood that any suitable cooling medium may assess? of thebore of the resistor at opposite sides thereof under compression tofrictionally support the resistor, and narrow strip-like. meanspositioned adjacent the end of the resistor and extending in a planeparallel to the tubular resistor, said wire members secured to saidstrip-like means to support said resistor with the strip-like meansoverlapping the resistor along the edge of the wall of the resistor tominimize the obstruction of the flow of air around and through theresistor.

'2. Mounting means for a tubular resistor having a central boreextending therethrough'comprising a singlepiece resilient Wire memberhaving a U-shape and forming two legs and a connecting portion, each legbent in a U-shape to form leg portions, said member fitting in the endof the bore with the leg portions in engagement with the wall of thetubular resistor and supporting said resistor under resilient pressure,strip-like means I extending; parallel to the axis of the tubularmember, fastening means on the other end of said wire member to securesaid resistor with the narrow edge passing the end of the wall ofsaid'tubular member to facilitate the airflow through and around theresistor.

3. A supporting means for a resistive member comprising'a tubular membersupporting said resistive member and having a central axial bore formedby a generally tubular shaped wall with an outer surface, strip-likemeans for supporting said tubular member at each end thereof, tworesilient substantially V-shaped plate members fitting in a respectiveend of said tubular member, each plate member having two thin plateportions extending longitudinally in said bore parallel to the axis andwall of said bore and secured along a common longitudinally extendingedge, said plate portions having longitudinally extending side edgesgenerally parallel to the common edge, said common and sideedgesengaging the wall of said bor'e'along spaced contact lines under theresilient pressure of said plate member to frictionally support saidtubular member, and fastening means. 011. j said plate member forsecuring saidtubular rne'mbe'r on saidstrip-like means with saidstrip-like means extending across said tubular member between the boreand the outer surface to permit the ready flow of air through and aroundthe tubular member supporting the resistive member to remove the heattherefrom.

4.. Mounting means as set forth in claim 2 in which said connectingportion is U-shaped and at an angle to I said, leg portions andpositioned inrelation to said striplike means so as to prevent saidresistor from engagin said'strip-like means.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Oct. 15, 193 1

